Modern driver assistance systems, such as lane keeping systems, automatic braking systems and the like, generally have a plurality of units for ascertaining an in particular instantaneous friction coefficient between wheels of the motor vehicle and the roadway. These so-called friction coefficient estimators are very specifically designed for different driver assistance units and are independent of one another. This has advantages with respect to the availability of the signals and the optimal design of the driver assistance system, and in particular of the individual driver assistance units of the driver assistance system. The respective unit includes a friction coefficient model, which may be formed by software and/or by hardware, and a sensor, which provides an input signal for the friction coefficient model. As a function of the input signal, the friction coefficient model determines the respective friction coefficient as an output signal. The driver assistance system is set or calibrated as a function of the ascertained friction coefficient in order to be able to respond optimally in an instantaneous driving situation, for example in order to initiate a safe braking process or to maximally brake wheels of the motor vehicle individually when negotiating curves without loss of static friction.